The present invention relates generally to imaging systems that use light sources such as infrared light for the purposes of transmitting image information from a camera to another device such as a computer system incorporating a light receiving device adapted to receive data.
Video cameras are used with computers for capturing images for uses such as video conferencing or storage. One difficulty in using a video camera in a typical office is caused by lighting. Offices often have overhead lighting which creates undesirable shadows that result in unsatisfactory image pickup.
Most digital or video cameras use a CCD (Charge Couple Device) as an electronic sensor to capture an image. Depending on the material of the CCD, it may have a wide radiometric spectrum ranging from blue (400 Nm) up to mid-infrared (2400 Nm) (the visible spectrum is from 380 to 780 Nm).
The most recent development in communication between computers and other data processing systems has been the use of infrared light to transfer data between the systems. Infrared transceiver communication systems are used to connect workstation computers, lap-top computers to each other and to other data handling system such as printers in the form of local access networks (LANs). These infrared LANs can provide similar capabilities to wired LANs without requiring wire connections. In addition, infrared communications have been adapted to transmit imaging data obtained by digital or video cameras to data processing systems such as computers for the purposes of video conferencing or further processing of the images.
Many companies have adopted the standards proposed by the IrDA (Infrared Data Association(trademark)) for the transmission and reception of data using infrared light. The infrared light wave lengths adopted for use under the IrDA guidelines is 870 nm. This is in the near infrared range (close to the visible spectrum). We have found that many CCD video cameras will respond to the infrared light near this wavelength. Infrared emitting LED""s (Light Emitting Diodes) are readily available that transmit infrared light in the same region and also can provide suitable infrared sources.
We have found that the following video cameras will respond readily to infrared light in this region:
1. Connectix QuickCam(trademark) from Connectix Corp. Connectix mounts and infrared filter in front of the CCD of the QuickCam video camera to filter out Infrared (IR) light. This is removed to permitted it to respond to IR light.
2. GBC CCD-506 from CCTV Corp. is a typical CCD based low light black and white surveillance camera.
3. Sony Video 8 Camcorder
Cameras in Low Light Conditions
While human vision can handle a wide latitude of light intensity (dark vs bright areas), CCDs are fairly limited. This creates problems when capturing an image of a person especially using overhead lighting. Dark shadows appear under the eyebrows. While the human eye differentiates these as only shadows, a CCD camera may see them as virtually black due to its limited ability to handle contrast.
The solution most used by the photographers to solve this problem is to provide an additional light source at or near the camera to illuminate the subject. This floods the subject with light minimizing the impact of overhead or poor lighting and reduces the contrast range of the lighting to permit satisfactory imaging.
In video conferencing or other applications which use live video, the image must be captured by the camera and sent to a computer or other data processing system. As discussed previously, one technique for communicating from camera to a computer (such as a PC) is to use infrared light.
We have found that it is possible to use the infrared light source that is used to transmit the image information from a video camera or a digital camera to a computer can also be used to illuminate the subject satisfactorily. The present invention provides an imaging system that can illuminate the subject satisfactorily with light such as infrared light from its infrared transmission source that is used to transmit information from the camera to an image recording or data processing system. Advantageously the system will include camera such as a video camera having an image sensor sensitive to visible and infrared light. A light emitting device such as an infrared LED (or an LED operating in the visible spectrum) is associated with the camera in order to transmit image data output from the camera. Preferably, the light emitting device is adapted to emit light or infrared light in a divergent beam.
Advantageously, the Light Emitting Device is positionable with respect to the camera so that it can illuminate a subject with its light within the field of view of the camera. Advantageously, the light emitting device can be positioned on the camera to project light forwardly to the subject or can be incorporated in a separate device which is connected to the camera and aimed at the subject in order to provide illumination.
In one aspect of the invention, a controller is provided for controlling the light emitter to transmit image data to the recording or data processing system at the same time as an image is being captured by the image sensor of the camera.
In another aspect of the invention, the controller can be adapted to permit the camera to capture an image at the same time as transmitting data of an image previously captured. Additional infrared light (such as in the form of false data) can be added to the transmission to provide improved illumination of the subject if required.
The infrared emitter can be mounted on the camera to point in the same direction as the lens.
Normally the camera will be used in conjunction with another unit of image processing or data processing equipment such as a computer which will itself have an infrared transceiver. The infrared transceiver of the computer can also be adapted to illuminate a subject being photographed by suitable placement thereof as will be understood readily by those skilled in the art.
Generally, in its broadest form, the invention uses the same infrared transceiver or emitter that is used for communication between camera and an auxiliary unit with which it is in communication to provide illumination of a subject being photographed so that there will be sufficient subject illumination for successful imaging.
When the infrared emitter of the camera is used to illuminate the subject at the same time as it is transmitting image data conservation of energy is achieved as no extra energy need be expended on illumination. This will enable the camera, which is typically battery powered, to be used for a longer period of time on each charge, or if powered from the mains will achieve it a reduction in energy expense.